In 1989, NIMH funded two national surveys of AIDS-related risk behaviors (MH46240, MH43892) that sampled respectively people 18-50 and 51-75 years of age. These two surveys were combined to form the National AIDS Behavioral Surveys (NABS). In NABS we have obtained data on 12,000 respondents (oversampling black and Hispanic respondents), and have conducted a nonresponse survey of a subsample of nonrespondents to the main study. The proposed study will build on our initial cross-sectional survey to produce a longitudinal study. Approximately 90% of baseline respondents volunteered for a potential one year follow-up interview. This longitudinal study will examine changes in respondents' sexual behaviors, HIV test-seeking, HIV-related beliefs, and intravenous drug use practices over a one year period. We will also test the AIDS Risk Reduction Model (ARRM, Catania et al., 1990) and generate data on patterns of sexual mixing across social strata. The findings will (a) aid in identifying segments of the national population defined by race/ethnicity, gender, marital status, age, social class) who continue to perform high risk activities, and delay HIV testing, (b) describe how (if) these segments change over time which, in turn, will indicate if there are new groups that should be targeted for intervention, (c) provide data relevant to intervention content development, (d) provide a rigorous longitudinal test of the ARRM, and (e) generate findings of import to questions of population spread of HIV (sexual mixing). These findings will be useful for developing HIV prevention programs and policy, and will form the basis for proposing subsequent surveys that will monitor HIV-related risk behaviors in the years to come.